The present invention relates in general to a cushioned brake beam wear plate, and in particular to a cushioned brake beam wear plate adapted to be mounted in a railroad truck side frame pocket to cushion the brake beam lug or extension head of a brake beam from high and low frequency vibration, impact shocks and severe upward and downward forces and thereby increase the life of the brake beam.
Braking systems on railroad car trucks include brake beams having brake shoes for engaging the wheels to apply braking forces. The railroad car trucks include guide brackets or pockets formed on the side frames of the trucks. Steel or plastic wear plates are mounted in the guide brackets to guide the movement of the brake beams. The brake beams include extensions, extension lugs, extension heads, paddles or brake beam lugs (hereinafter referred to as xe2x80x9clugsxe2x80x9d or xe2x80x9cbrake beam lugsxe2x80x9d) at opposite ends which are guidingly received in the slideways of the steel or plastic wear plates.
Plastic wear plates having self-lubricating characteristics are preferably used to overcome the potential wear problems on the brake beam lugs. An example of a plastic wear plate is disclosed in U.S. Pat. No. 4,471,857. This patent discloses a plastic wear plate having a thin rubber coating of natural rubber that preferably has a thickness in the range of from about 0.015 inch to about 0.020 inch. The thin rubber coating is suitably bonded to the exterior surface of the walls of the wear plate or integrated with the polymeric material so as to be in one piece integral relation therewith. The thin rubber coating is used to increase the friction between the plastic wear plate and the steel guide bracket to prevent the displacement of the wear plate from the guide bracket. A further plastic wear pad is provided in U.S. Pat. No. 5,692,964 which discloses a plastic brake beam wear pad for solving brake beam droop and cold flow problems (as described therein) which cause uneven wear of the brake shoes.
Railroad car truck side frames are not protected by springs or other cushioning mechanisms. As railroad cars move along the tracks or rails through varying terrain and at various speeds, the railroad car truck side frames and the guide brackets or pockets are subject to high and low frequency vibration, to impact shocks and to severe and sudden upward and downward forces. The forces can be as great as four to six times the pull of gravity (xe2x80x9cG""sxe2x80x9d). The known steel and plastic brake beam wear plates do not adequately insulate the brake beam lugs from the vibration, shocks or forces. The brake beam lugs are thus continuously subjected to the vibration, shocks and forces during train movement. This can cause increased deterioration or wear of the brake beam and the brake beam lugs, cracks in welds in the brake beam and loosening of the riveted trusses which hold the brake beam. Accordingly, there is a need for a device which substantially dampens the high and low frequency vibration, impact shocks and sudden and severe upward and downward forces in the guide brackets or pockets of the railroad car trucks.
The present invention provides a cushioned brake beam wear plate that overcomes the above problems by absorbing high and low frequency vibration, shocks and sudden and severe upward and downward forces in the guide bracket or pocket of a railroad car truck. The cushioned brake beam wear plate of the present invention includes a substantially U-shaped member having upper and lower walls connected by an end wall and is preferably formed from a polymer material resistant to cold flow. The lower wall is thicker than the upper wall. A thick cushioning pad which is preferably rubber is positioned on the exterior side of the lower wall to dampen the high and low frequency vibration, impact shocks and severe upward and downward forces in the guide bracket. The cushioning pad may be bonded, glued, fastened or otherwise attached to the wear plate. The cushioning or rubber pad on the bottom wall has a suitable thickness and elasticity to cushion the brake beam lug received in the wear plate from vibration, shocks and forces in the guide bracket or pocket.
It is therefore an object of the present invention to provide a cushioned brake beam wear plate.
A further object of the present invention is to provide a cushioned brake beam wear plate which dampens the vibration, shocks and forces on the brake beam lug received in the wear plate.
Other objects, features and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of drawings, wherein like numerals refer to like parts.